Flu vs Cold: How to Tell the Difference
Influenza and the common cold share some symptoms but are actually caused by different viruses and can have very different outcomes. The flu can be serious — particularly in children, the elderly, and people with chronic conditions — while a cold is usually mild. This guide helps you tell the difference and know when to see a GP.
Key Symptom Differences
- Onset: Flu comes on SUDDENLY (within hours). A cold develops GRADUALLY over 1–2 days.
- Fever: Flu typically causes a high fever (38°C or above) lasting 3–4 days. Colds rarely cause fever in adults.
- Body aches: Severe with the flu, often debilitating. Mild or absent with a cold.
- Fatigue: Flu causes extreme fatigue and weakness that can last 2+ weeks. Colds cause only mild tiredness.
- Headache: Common and severe with the flu. Rare with a cold.
- Runny nose and sneezing: Hallmark of a cold. Less prominent with the flu.
- Sore throat: Common with both but usually milder with the flu.
- Cough: Both, but flu cough is usually dry and can persist for weeks.
The Simple Test: How Bad Do You Feel?
The most reliable way to distinguish flu from a cold is severity. If you feel like you have been “hit by a truck” — you cannot get out of bed, you have a high fever, your muscles ache — that is almost certainly the flu. If you are still able to go about your day with just a runny nose and sore throat, it is most likely a cold.
When to See a GP
Most colds and even mild flu can be managed at home with rest, fluids, and over-the-counter symptom relief. See a GP promptly if you:
- Are in a high-risk group: over 65, pregnant, chronic illness, immunosuppressed
- Have a fever lasting more than 3 days or above 39°C
- Are having difficulty breathing or have chest pain
- Cannot keep fluids down and are becoming dehydrated
- Have a child under 3 months with a fever
- Have symptoms that started to improve then got worse (may indicate secondary bacterial infection)
- Have a persistent cough that is producing green or bloody mucus
- Have confusion, severe dizziness, or seizures
Antiviral Medications for Flu — the 48-Hour Window
Antiviral medications like oseltamivir (Tamiflu) can reduce the severity and duration of influenza, BUT they must be started within 48 hours of symptom onset. If you suspect flu and are in a high-risk group, contact your GP or mygponline.com.au telehealth immediately — do not wait for symptoms to peak.
Prevention: The Annual Flu Vaccine
The flu vaccine is the single most effective way to prevent influenza. It reduces your risk of contracting flu by 40–60% and dramatically reduces the risk of severe illness if you do catch it. It is free under Medicare for over-65s, pregnant women, children 6 months to 5 years, Aboriginal and Torres Strait Islander people, and people with chronic conditions. See our flu season guide for more.
Could It Be COVID-19?
COVID-19 symptoms overlap significantly with both flu and cold. If you have cold or flu symptoms, take a rapid antigen test (RAT) — they are widely available at pharmacies. A positive RAT means you should isolate and contact a GP if you are in a high-risk group. Telehealth consultations are ideal for COVID assessment since you do not need to expose others.
Find a Family Doctor Clinic Near You
If you are unwell and unsure what to do, a GP visit (in person or telehealth) is always a safe option. Family Doctor clinics across Australia offer same-day appointments for acute illness.
Frequently Asked Questions
How long does the flu last?
Most healthy adults recover from flu within 7–10 days, though fatigue and cough can linger 2–3 weeks. High fever typically breaks within 3–4 days. A cold, by comparison, usually resolves within 7–10 days with milder symptoms throughout.
Can I get flu and a cold at the same time?
Yes, but rarely. Most “flu-like” illnesses are actually caused by one dominant virus at a time. If your symptoms seem to combine both — or worsen after initial improvement — see a GP, as this may indicate a bacterial complication like sinusitis or pneumonia.
Should I take antibiotics for a cold or flu?
No. Antibiotics only work against bacterial infections. Both colds and influenza are caused by viruses and do not respond to antibiotics. Overuse of antibiotics for viral illness drives antibiotic resistance. Your GP may prescribe antibiotics if you develop a secondary bacterial infection (e.g. pneumonia after flu).
How can I protect others when I am sick?
Stay home from work or school. Cover coughs and sneezes with a tissue or your elbow. Wash your hands frequently. Wear a mask if you need to be around others. You are most contagious in the first 3–4 days of illness.